The objective of this project is to elucidate the mechanisms underlying cellular remodeling in two cell types in response to two different agents. 1) The production of elongate processes by L-cells in response to cyclic AMP as described in the previous annual report on this project and 2) the change in fine structure associated with shape changes by Fc receptor-bearing lymphocytes in response to binding of antigen-antibody complexes on a plastic surface. Time lapse photographs and standard techniques of electron microscopy are combined with treatment with various drugs affecting the shape changes.